1. Field of the Invention
The present invention relates to a pouring plug used for paper containers filled with juice, milk and the like.
2. Description of the Prior Art
A conventional pouring plug of this kind comprises a substantially cylindrical pouring member having a flange corresponding to a peripheral surface portion of a fitting hole formed in a container body and a cap threadedly attached so as to cover the pouring member, the pouring plug being fitted into the fitting hole from inside of the container body.
As shown in FIG. 8, a pouring plug 100 of this kind comprises a substantially cylindrical pouring member 101 and a cap 103 threadedly attached so as to cover a cylindrical portion 102 of the pouring member 101. In the pouring member 101, a shoulder 104 is located at a base end of the cylindrical portion 102, the shoulder 104 being registered with a fitting hole B of a container body A, and the shoulder 104 being integrally provided therearound with a flange portion 105 corresponding to a peripheral surface (an inner surface side) of the fitting hole B (See, for example, Japanese Utility Model Application No. 62-62515 (Japanese Utility Model Application Laid-Open No. 63-169429) previously filed by the present applicant). This flange portion 105 is secured to the container body A by ultrasonic deposition, for example, as will be described hereinafter. The cylindrical portion 102 of the pouring member 101 is interiorly integrally provided with a lid 107 through a thin-wall portion 106. By pulling a pull-ring 108 provided on the lid 107, the thin-wall portion 106 is torn to remove the lid 107 and the container is opened.
As a device used for liquid paper-containers similar to that described above, there is a pouring plug 109 having a small height dimension, as shown in FIG. 9. This pouring plug 109 is constructed so that a lid 112 is integral with a top portion 110 having a projected shape through a thin-wall portion 111, and the thin-wall portion 111 is torn and opened by pulling up a pull ring 113 provided on the lid 112 in a manner similar to the case of the aforementioned pouring member 101. The lid 112 is turned through a self-hinge portion 114 positioned at the base end of the lid 112 to open and close an opened opening. The top portion 110 is integrally provided in its outer peripheral portion 115 with a flange portion 116, the flange portion 116 being secured to the container body in a manner similar to that described above.
Projecting portions a are integrally provided, as shown, in the vicinity of the flange portion 116 of the pouring plug 109. The projecting portions a have a small height dimension and are at the shoulder 104 of the pouring plug 100 of the type having the cylindrical portion 102 as described above, whereby the inner peripheral edge of the fitting hole B of the paper container body A is held by the projecting portions a and the flange portions 105 and 116 when the pouring plug is temporarily mounted for reasons to be described later.
In mounting the pouring plug from inside of the container body as described above, it is mounted and fixed by depositing the flange portion onto the peripheral surface of the fitting hole by, for example, ultrasonic vibrating deposition, heat seal or the like. As disclosed in Japanese Patent Publication No. 60-50,139, Japanese Utility Model Application Laid-Open No. 61-100,517, U.S. Pat. No. 4,788,811 specification, Japanese Patent Publication No. 64-2,505, etc., the step of mounting a pouring plug to a container body is included in a series of steps including the assembly of a flat sleeve (prior to formation of a bottom portion of a container body), filling contents, and heat seal of a top of a container body. As shown in FIG. 10, a flat-state sleeve 117 is supplied to a line from an assembly of the sleeve to the heat seal of the top of the container body, and the assembly of the sleeve 117 is sequentially carried out (Step I). After the sleeve 117 has been assembled into a rectangular shape, the bottom portion is formed (flaps at the bottom are cemented) (Step II).
Next, the pouring plug 100 is fitted on the container body A in which the bottom is formed and the top is opened (Step III). In this Step III, for example, a plurality of pouring plugs 100 in an aligned state are supplied by a guide 118 (for example, see the aforesaid U.S. Pat. No. 4,788,811 specification), the pouring plugs are removed one by one by a sucker 119 with vacuum action, and the sucker 119 with the pouring plug 100 held thereon is inserted from the opened top of the container body A held in a predetermined position. The sucker 119 inserts the pouring plug 100 from inside into the fitting hole B of the container body A, and the pouring plug 100 is arranged. A pad-plate not shown is applied to the outer portion of the fitting hole B (Step IIIa).
When the pouring plug 100 is arranged in the fitting hole B, the container body A is moved to an ultrasonic depositing machine 120 (Step IIIb).
When the container body A reaches a final fitting position of the pouring plug 100, an anvil 121 enters from the top of the container body A, a horn 120a of the ultrasonic depositing machine 120 is applied around the fitting hole B, and the ultrasonic deposition is carried out wherein the flange portion 105 of the pouring plug 100 and the container body A are held by the anvil 121 and the horn 120a (Step IIIc).
Upon termination of fitting and fixing of the pouring plug 100, the container body A is moved to a liquid filling machine 122, and filling is effected at a predetermined position (Step IV).
Upon termination of filling, the container body a is moved, and the top of the container body A is sealed at a predetermined position by a device 123 such as a sealer (Step V).
During the ultrasonic deposition of the pouring plug after the pouring plug has been arranged in the fitting hole, that is, the container body is moved in the aforesaid Step IIIb, it is necessary to prevent the pouring plug from being displaced or slipped out due to vibrations caused by said movement. When the pouring plug is displaced or slips out, there arises situations such as subsequent ultrasonic deposition cannot be positively carried out, a defective deposition of the pouring plug occurs, or the operation of the ultrasonic depositing machine has to be stopped.
In view of the above, a device has been made to temporarily fix the pouring plug to the container body. This is a technique in which as described above, the projecting portions are provided, at a height position having a paper-thickness dimension from the flange portion, on the peripheral edge at the lower position of the cap and on the peripheral edge at the lower end of the cylindrical portion of the pouring member (for example, see Japanese Utility Model Publication No. 61-7147).
The problem posed here is that these pouring plugs are generally manufactured of relatively soft synthetic resins such as high-density polyethylene. As described above, a dimension d1 between the projecting portion a and the flange portion 105 is the same as a paper thickness d2 of the container body, as shown in FIG. 11. Therefore, when the pouring plug is inserted and arranged into the fitting hole, the projecting portion a impinges upon an inner peripheral edge C of the fitting hole B and becomes deformed whereby the peripheral portion of the fitting hole cannot be held by the projecting portion a and the flange portion 105. Furthermore, there arises a state where the deformed projecting portion a cannot be completely withdrawn on the surface side.
Because of this, the pouring plug slips out during the movement in the aforesaid Step IIIb despite the provision of a device with a projecting portion intend to prevent the pouring plug from being displaced or from slipping out.
On the other hand, when the pouring plug is forcibly pushed to move the projecting portion on the surface side by the method of increasing the pressing force of the sucker, the inner peripheral edge C of the fitting hole B becomes scratched as shown in FIG. 12 because the container is made of paper, posing an inconvenience of being unattractive in external appearance.
From the foregoing, there is contemplated that a pouring plug molded from a synthetic resin which is harder than the high density polyethylene generally used (that is, the hardness of the projecting portion is enhanced).
According to the means for making the projecting portion harder, the projecting portion is small in deformation and is withdrawn on the surface side and can be positively engaged. However, conversely, the inner peripheral edge C of the fitting hole B is cut, being unattractive in external appearance.
Similarly, even if the projecting portion is sharpened to facilitate withdrawal of the projecting portion on the surface side or the length of the projecting portion is lengthened along the circumference to make engagement positive, the inner peripheral edge C of the fitting hole B becomes unfavorably scratched because of the paper-made container.
Another problem lies in that the pouring plug has its flange portion deposited by the ultrasonic depositing machine as described above. However when deposited, ultrasonic vibrating energy tends to be concentrated on the aforementioned thin-wall portion, and therefore the thin-wall portion becomes dissolved thereby producing pin holes.